Forgetting Memory’s Weaknesses
Written by: Elisa Dong ‘24
Edited by: Meehir Dixit ‘24
If you catch someone in the act of a crime, common sense suggests that the case is good as closed. After all, isn’t eyewitness testimony one of the most reliable forms of evidence? While this faith in witness testification is common, it isn’t so sensible. According to studies by the Innocence Project, a nonprofit legal organization seeking to exonerate innocently convicted individuals, mistaken eyewitness identifications actually contributed to 69% of the more than 375 wrongful convictions in the United States later overturned by DNA evidence .
Memory is simply our brain’s way of storing information. We may be able to “play back” memories in our mind, but the nature of memory is closer to stories cobbled from what we notice than unmalleable video recordings of the world around us. New memories aren’t just taken out of context; they’re integrated with our mind’s existing body of knowledge, a concept known as memory’s ‘bias’ . This is strikingly represented in the phenomena of cross-race bias and own-race bias, in which people are much better at distinguishing faces of their own race as opposed to others . Of the 358 false identifications resulting in a death sentence reported by the Innocence Project in 2018, 41% involved cross-racial misidentifications– 221 of the 358 people were African American [1, 4].
The malleability of memory is emphasized during the process of retrieval. Consolidation occurs when memories are first formed and stored in the brain. These memories are not rigid, however— when they are called up and then stored back in the brain again, they become malleable while undergoing what is known as “reconsolidation.”
In one study, participants were shown a video of a car accident, and then questioned about what happened. When asked “How fast were the cars going when they smashed into each other?”, as opposed to “How fast were the cars going when they hit each other?”, participants were more likely to recall broken glass— despite there not being any such broken glass at the original site . Biased language can affect recall and manipulate memories in a particular direction, even when done so unwittingly.
The neurological basis for memory relies on the idea that memory is defined by the strength of connections in a network. Long-term potentiation (LTP) enhances synaptic strength, while long-term depression (LTD) weakens these connections. LTD can occur when neurons fire in an uncorrelated way, as in the case of neurons individually activating memories of different experiences. These different types of stimulation can alter the strength of synapses, allowing new information to overwrite old information and making it possible for memories to interfere with each other .
The competition between new and old memories is seen in cases of overlapping memories. When two memories share similarities, attempting to retrieve the original event can actually mix in information from the second event. Rats given a foot shock will “freeze” in fear, responding to the same context in which they were given the shock. In one study, rats were exposed to two different contexts, A and B, over the course of several days (you can think of a “context” as a specific environment, such as being placed into two distinct boxes), allowing them to form an association between the two contexts. Then, the rats were given a shock in context B. Despite the shock having only occurred in context B, they displayed more fear in context A than a totally foreign context C. This study from Concordia University reinforces the idea that the memory of context A “spilled over” into the shock that occurred in context B, forming a false connection between A and B .
Why does our brain even allow old memories to be changed? There are functional benefits: being able to update old, faulty memories, strengthen them, or even weaken them can be useful for survival. Memories are, after all, nothing more than the pool of information we collect and then use to best guide our future actions. In critical situations like court cases, however, where even the smallest details can change outcomes (think of the study with the car crash— perceiving someone as driving faster before the accident would net them a higher fine in court!), human memory cannot be relied upon as the sole arbiter.
Organizations like the Innocence Project have made suggestions for eyewitness identification reform including policies such as blind administration, fillers in lineup composition, and less explicit guidance for witnesses . Other groups hope to dispel the myth that memory is immutable in the eye of the public. In one study conducted via Mechanical Turk in 2012, 46.9% of the US participants agreed with the statement “Human memory works much like a video camera, accurately recording the events we see and hear so that we can review and inspect them later,” despite such views being contested by professionals for decades . The ramifications of false beliefs about memory’s reliability can extend beyond harmless pseudoscience and into courtroom injustice. While our memories may serve us just fine in day-to-day life, we must acknowledge that they aren’t always accurate and inform those that may think otherwise.
1. Innocence Project. Eyewitness Identification Reform. Retrieved Nov 25, 2020. Available from: https://innocenceproject.org/eyewitness-identification-reform/
2. Schacter DL. The Seven Sins of Memory (How the Mind Forgets and Remembers) Houghton Mifflin Company; 2001. Available from: https://books.google.com/books?hl=en&lr=&id=m8qMjPF1NYAC&oi=fnd&pg=PP1&ots=UI5YimI-Nb&sig=wE-Wd1-w79hbxaMYj9GS7mHRVXw#v=onepage&q&f=false
3. Goldinger SD, Yi H, Papesh MH. Deficits in cross-race face learning: Insights from eye movements and pupillometry. Journal of Experimental Psychology: Learning, Memory, and Cognition, 35(5), 1105–1122. DOI: https://psycnet.apa.org/doi/10.1037/a0016548
4. Chew SL. Myth: Eyewitness Testimony is the Best Kind of Evidence. Association for Psychological Science. August 20, 2018. Available from: https://www.psychologicalscience.org/teaching/myth-eyewitness-testimony-is-the-best-kind-of-evidence.html
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